Yanmar engine issues

[Fr J Hackett]

Perhaps it is something to do with your charge splitter. I had a similar setup with my Bavaria 33, albeit with a 30 hp engine. 5*95ah batteries in 3 banks, one for engine, 3 for house and one for bow thruster/windlass. Volvo D1 30 with a 115amp alternator charging through a 3 way Cristec splitter. Never any problem such as you describe because, I think the splitter first charges the start battery (which takes minutes, or even seconds, then the house and then the forward battery, In reality the house is the only one that really demands a big charge. Do you have a battery monitor which will tell you how much is going into the house bank on start up?

As a sort of aside Yanmar used to fit an alternator cutout for startup on the 1GM when fitted with a saildrive because the added drag of the saildrive oil was enough to make starting and cold running difficult. Maybe it is something to do with the fuelling at low revs and the minimal power the engine produces that tips it over the edge compared with a Volvo. BTW I never consciously needed the glow plugs on the Volvo as it always started immediately after turning on in in UK winter weather.

The OP has stated that it takes 45 seconds to "warm up" or reach a condition where he can or the motor will run up above 1000RPM after that everything apparently is OK, furthermore disconnecting the alternator allows the engine to achieve greater than 1000RPM instantly, he says.
He makes no mention of what his battery configuration is or whether he has a splitter VSR or other means or indeed whether he has an external regulator ( I am guessing that he doesn't have the latter)nor does he say if he has a battery management / charge indicator.
The issue is connected with the alternator of that there is no doubt as he has confirmed that in the absence of the alternator the engine immediately revs up. The logical explanation is that the alternator is instantly outputting its full charging capability until its own internal regulator senses the charge state of the battery and in doing so absorbed power from the engine when it reduces the output the power required to drive the alternator drops accordingly. This will happen regardless of which batteries the alternator is driving it is a function of the delay in the internal regulator of the alternator sensing and then regulating the alternators output. It is not an ideal situation and one that could be overcome by fitting a decent smart regulator. It may be that there is a problem with the internal regulator of the Hitachi alternator and it should be capable of delaying the output but that seems unlikely.
There does remain the problem of course what happens if all the batteries are at a very low state of charge and the alternator is trying to deliver it's maximum output if what I have concluded is the problem then in such circumstances the engines power output is likely to be compromised, figures have already been quoted of a 20% plus power loss, not a good situation. Which leads me to question should a 20Hp engine be fitted with a 125 A alternator? Some years ago I re-engined with a 3YM30AE which was delivered with a 60A Hitachi alternator as standard! I did replace it with a high output Balmar and the ARS-5 smart regulator though. Is the fitting of 125A alternators a new thing? and your comment about a cutout presumably suppressing field current sounds logical on such a setup.

 

[greeny]

4 tests I would do before running off down the road of changing anything and spending money.
System all normal, put in gear, Increase revs, what happens. - Engine slow to respond and build revs. is what I understand. (Engine has load of prop and alternator.)
System all normal, in neutral , increase revs, what happens? (alternator load only)
Disconnect alternator belt.
Put in gear, increase revs, what happens? (engine load only)
Put in neutral, increase revs, what happens? (absolutely no load). - revs freely?
It's not going to pin point your problem but will clarify when the problem occurs.
You may have already done them, if so, ignore me.
I would also use whatever means I could, SSR lists, Jeanneau dealers, etc to locate other "same" boat owners and try to contact them direct with the question of whether they have the same problem.
I know you don't agree but I'm still thinking fuel/ governor a possibility.

 

[Fr J Hackett]

4 tests I would do before running off down the road of changing anything and spending money.
System all normal, put in gear, Increase revs, what happens. - Engine slow to respond and build revs. is what I understand. (Engine has load of prop and alternator.)
System all normal, in neutral , increase revs, what happens? (alternator load only)
Disconnect alternator belt.
Put in gear, increase revs, what happens? (engine load only)
Put in neutral, increase revs, what happens? (absolutely no load). - revs freely?
It's not going to pin point your problem but will clarify when the problem occurs.
You may have already done them, if so, ignore me.
I would also use whatever means I could, SSR lists, Jeanneau dealers, etc to locate other "same" boat owners and try to contact them direct with the question of whether they have the same problem.
I know you don't agree but I'm still thinking fuel/ governor a possibility.

You have a point in that the governor is not set up to be able to cope with the added load of a 125A alternator which brings me back to the point about a 20Hp engine trying to drive a 125A alternator.

 

[Lightwave395]

Probably not a fair comparison but I've got a 5 year old 3YM30 with the electronic control panel and a 125A alternator charging a 70A engine start battery and 2 X 115A service batteries, they're connected through a Sterling pro-split and this lot delivers instant power to the prop when the engine starts hot or cold.

Possibly more useful I've got a spare hardly used Hitachi 55A alternator from my old 3GM30 in the garage you could try if you're anywhere near the IOW...

 

[Adjag]

Can I enquire how many battery banks and batteries you have? We have 3 banks and 5 batteries. 1 engine, 2 domestic, 2 windlass.

Could I be so bold as to ask you to disconnect your shore power and run down your domestic batteries to less than 80% and time the startup?

Like you, we like to warm the engine up before use, but this has hidden the problem for some time and unlike you we have no confidence that if we misjudged our position that a quick engine start and burst of power would happen/save us.

As no one else seems to be complaining we wonder if there is a problem in our individual boat.

We have less battery capacity than you, one engine plus (until recently - another story!) 2*160Ah AGM house batteries. I have a shunt on the house batteries and the alternator does give its full 125A above about 1100rpm when they're well discharged, so I don't think your extra batteries are causing the problem. Your tests have shown it's not the engine so it must be the alternator & batteries.
Yes I can do the test you suggested but not for a week or 2 (normal life getting in the way), but on a cold start with discharged batteries I wouldn't be at all suprised if it takes 45s. As others have said it's a big alternator on a little engine but I find it great to have this big output to recharge the batteries after a few nights on the hook. We bought the bolt from new and the dealer suggested at the time an alternator regulator with "soft start" might help, but I decided to live with it in the name of simplicty.

For us it's never been a problem over the last 4yrs, I just let it warm uo before asking anything of it. I guess this could be a problem if the anchor dragged in the middle of the night? Critically though ours is fine when the engine is warm, whereas it seems yours isn't and I can understand (I'd have hit that bouy) your concern about that.

If you want to improve things it seems to me an external regulator with, say, 45s soft start delay - Balmar amongst others make them.

ps I found this intersting when reseaching the problem after getting the boat When Do You Need A High-Output Alternator? - Practical Sailor "There is also a 1 minute soft ramp-up which brings on alternator power gradually. It also helps prevent the engine from stalling if you frequently charge at idle. This is particularly important with small engines ... big alternators"

 

[Rhubarb]

It's still hard to believe that a single battery charging alternator is swallowing most of the power from a 18 hp diesel.

Will it quickly give a good burst of revs and power to the prop in gear with the belt removed? Not just rev in neutral.

Yes it will give a burst of revs with the alternator removed.
It will also reach full revs in gear (3600 revs) it just takes a while to get there.

 

[Rhubarb]

Perhaps it is something to do with your charge splitter. I had a similar setup with my Bavaria 33, albeit with a 30 hp engine. 5*95ah batteries in 3 banks, one for engine, 3 for house and one for bow thruster/windlass. Volvo D1 30 with a 115amp alternator charging through a 3 way Cristec splitter. Never any problem such as you describe because, I think the splitter first charges the start battery (which takes minutes, or even seconds, then the house and then the forward battery, In reality the house is the only one that really demands a big charge. Do you have a battery monitor which will tell you how much is going into the house bank on start up?

As a sort of aside Yanmar used to fit an alternator cutout for startup on the 1GM when fitted with a saildrive because the added drag of the saildrive oil was enough to make starting and cold running difficult. Maybe it is something to do with the fuelling at low revs and the minimal power the engine produces that tips it over the edge compared with a Volvo. BTW I never consciously needed the glow plugs on the Volvo as it always started immediately after turning on even in UK winter weather.

The charge splitter was initially blamed and a voltage sensing relay tried. The test managed to prove that a voltage sensing relay was not the solution and the charge splitter was not the problem,

 

[Fr J Hackett]

Yes it will give a burst of revs with the alternator removed.
It will also reach full revs in gear (3600 revs) it just takes a while to get there.

Is that with the alternator removed

 

[Rhubarb]

4 tests I would do before running off down the road of changing anything and spending money.
System all normal, put in gear, Increase revs, what happens. - Engine slow to respond and build revs. is what I understand. (Engine has load of prop and alternator.)
System all normal, in neutral , increase revs, what happens? (alternator load only)
Disconnect alternator belt.
Put in gear, increase revs, what happens? (engine load only)
Put in neutral, increase revs, what happens? (absolutely no load). - revs freely?
It's not going to pin point your problem but will clarify when the problem occurs.
You may have already done them, if so, ignore me.
I would also use whatever means I could, SSR lists, Jeanneau dealers, etc to locate other "same" boat owners and try to contact them direct with the question of whether they have the same problem.
I know you don't agree but I'm still thinking fuel/ governor a possibility.

I was convinced it was a governor issue until the engine worked fine when the alternator was disconnected. As the boat will rev to 3000+ rpm (in time) and drive the boat in excess of 6 knots I cannot see it being a fuel problem.

 

[Rhubarb]

Is that with the alternator removed

Nope, that is with the alternator connected, it just takes time to get there.

 

[Rhubarb]

We have less battery capacity than you, one engine plus (until recently - another story!) 2*160Ah AGM house batteries. I have a shunt on the house batteries and the alternator does give its full 125A above about 1100rpm when they're well discharged, so I don't think your extra batteries are causing the problem. Your tests have shown it's not the engine so it must be the alternator & batteries.
Yes I can do the test you suggested but not for a week or 2 (normal life getting in the way), but on a cold start with discharged batteries I wouldn't be at all suprised if it takes 45s. As others have said it's a big alternator on a little engine but I find it great to have this big output to recharge the batteries after a few nights on the hook. We bought the bolt from new and the dealer suggested at the time an alternator regulator with "soft start" might help, but I decided to live with it in the name of simplicty.

For us it's never been a problem over the last 4yrs, I just let it warm uo before asking anything of it. I guess this could be a problem if the anchor dragged in the middle of the night? Critically though ours is fine when the engine is warm, whereas it seems yours isn't and I can understand (I'd have hit that bouy) your concern about that.

If you want to improve things it seems to me an external regulator with, say, 45s soft start delay - Balmar amongst others make them.

ps I found this intersting when reseaching the problem after getting the boat When Do You Need A High-Output Alternator? - Practical Sailor "There is also a 1 minute soft ramp-up which brings on alternator power gradually. It also helps prevent the engine from stalling if you frequently charge at idle. This is particularly important with small engines ... big alternators"

From what you describe it does sound like you have similar issues if not quite so serious. I will be interested in your test results.

 

[Fr J Hackett]

I was convinced it was a governor issue until the engine worked fine when the alternator was disconnected. As the boat will rev to 3000+ rpm (in time) and drive the boat in excess of 6 knots I cannot see it being a fuel problem.

Whilst I think it unlikely it could be a governor problem especially if it is a mechanical one.

Have you ever tried to charge a deleted battery bank and if so were the revs compromised?

 

[Rhubarb]

Whilst I think it unlikely it could be a governor problem especially if it is a mechanical one.

Have you ever tried to charge a deleted battery bank and if so were the revs compromised?

The lowest we’ve taken the house batteries is 70%. The batteries have all been checked by engineers and they are all functioning correctly.

 

[Rhubarb]

Which leads me to question should a 20Hp engine be fitted with a 125 A alternator?

That is what I’m wondering, it’s the Yanmar standard, but that doesn’t make it right.

 

[Poecheng]

It would be amazing if the extremely high load created by the oversized-alternator with no soft start was so perfectly balanced as to permit the engine to idle (but not stall) and yet not allow the revs to rise at all for a fixed period, when all of a sudden it can then rise as much as you wish it to.
I am not suggesting it is nothing to do with the alternator but it would be quite a feat to achieve such an unusual equilibrium simply by the application of load.
Being a bit dim here but, if the output matches the load, the application of the throttle brings about an increase in output - the load doesn't prevent revs rising unless the load itself increased massively to strangle the engine down. Though I don't know how you strangle a diesel engine down back to idle revs by application of load.
It is as if there is a soft start, just that it is on the throttle not the alternator

 

[Fr J Hackett]

That is what I’m wondering, it’s the Yanmar standard, but that doesn’t make it right.

I still think that the answer is most probable that the engine from cold struggles with the additional load of the alternator but as soon as it's begun to warm up and of course the alternator load is reduced then it can function correctly. It's a bit like having a bag or a load of seaweed around the prop it puts a load on the engine and the revs drop.
When you consider that the load by the alternator at full output is over 20% of the engines capacity then it is not surprising it struggles under those conditions. If I am correct in this then you may never actually be able to utilise the full output of the alternator without compromising the power delivered to the prop shaft which seems counterproductive although such times are rare and short. A smart regulator such as the Balmar would still allow the alternator to try to output it's maximum charge but it would then manage the alternator including its ability to deliver charge. It would certainly help with the initial situation. As you never seem to allow the batteries to discharge below 70% maybe if the initial "problem" is resolved then you could live with it but then again if you have a 125A alternator you would want to access it full charging capability without compromising the yachts propulsion.

 

[Poecheng]

The theory of high alternator load preventing the engine revs to rise is premised on the alternator belt fighting the power and torque of the diesel engine and winning. That surely would be some alternator belt set up.

 

[Fr J Hackett]

The theory of high alternator load preventing the engine revs to rise is premised on the alternator belt fighting the power and torque of the diesel engine and winning. That surely would be some alternator belt set up.

It happens and it's why devices have in the past been used to disconnect the field current to allow the engine to attain revolutions it's what smart charge controllers do. I wonder if there is evidence of belt slippage ? It would be interesting to see the actual output from the alternator over the 45 second period when the engine revs are compromised.

 

[Poecheng]

It happens and it's why devices have in the past been used to disconnect the field current to allow the engine to attain revolutions it's what smart charge controllers do. I wonder if there is evidence of belt slippage ? It would be interesting to see the actual output from the alternator over the 45 second period when the engine revs are compromised.

I agree as far as it goes and have had Adverc in the past - you can hear the load coming on and it may dip the revs a little but not much though it may make the engine work harder at those revs. There are soft starts and also with Balmar (as well as the programed limits) you can have a switch to almost turn the alternator off if, for example, you need max speed and all power to the prop.
Belt slip normally (I believe) is a hard-to-turn alternator but, for this theory, we have a perfectly gripping alternator pulley able to hold back the increasing power of a diesel engine via a belt and a perfectly gripping engine pulley ie the opposite to what normally occurs and when you get belt squeal. Last engine had a poly belt on a 20hp Beta but I would be surprised if the belt could hold the engine back to any great extent.
Calculations have been done for alternator load but this engine is at full throttle and should, therefore, be producing 20hp or thereabouts. Still trying to get my head round it but surely the throttle and the consequent fuel delivery dictates the power - we don't wait for a load to come off before we increase revs .

 

[Fr J Hackett]

I agree as far as it goes and have had Adverc in the past - you can hear the load coming on and it may dip the revs a little but not much though it may make the engine work harder at those revs. There are soft starts and also with Balmar (as well as the programed limits) you can have a switch to almost turn the alternator off if, for example, you need max speed and all power to the prop.
Belt slip normally (I believe) is a hard-to-turn alternator but, for this theory, we have a perfectly gripping alternator pulley able to hold back the increasing power of a diesel engine via a belt and a perfectly gripping engine pulley ie the opposite to what normally occurs and when you get belt squeal. Last engine had a poly belt on a 20hp Beta but I would be surprised if the belt could hold the engine back to any great extent.
Calculations have been done for alternator load but this engine is at full throttle and should, therefore, be producing 20hp or thereabouts. Still trying to get my head round it but surely the throttle and the consequent fuel delivery dictates the power - we don't wait for a load to come off before we increase revs .

It's all a bit chicken and egg but I can see a situation where the governor ( mechanical) is restricted by the alternator load holding the engine back until either the load decreases as the alternators regulator kicks in or the engine gradually overcomes the alternator load and the governor responds but for me it all starts with an initial loading by the alternator.